In hospital environments the transport of patients on a hospital patient support or of the hospital patient supports themselves is required. For this reason patient supports are fitted with a system of casters allowing handling. But the handling of heavy patient supports or patient supports with a patient can be physically uncomfortable. For this reason hospital patient supports are equipped with additional systems for propelling a patient support, for example in the form of a motorized wheel making patient support transport easier for hospital personnel. The aforementioned system constitutes a known state of art, for example according to U.S. Pat. No. 5,806,111, U.S. Pat. No. 6,505,359 or U.S. Pat. No. 7,090,041.
The motorized wheel is connected to the undercarriage and can be forced against the ground for the purposes of motorized movement or retracted into the undercarriage for the purposes of handling the patient support without engagement of motorized movement, as in patent application EP2298263.
One important element of the system for propelling a patent support is its control equipment. In one common embodiment, such as in the U.S. Pat. No. 6,330,926, the patient support is equipped with push bars having a mechanical switch by which the user activates the motorized movement of the patient support. Another of the alternatives according to U.S. Pat. No. 6,752,224 is the control of the drive system via push bars equipped with force sensors located between the push bars and the patient support. These sensors convert the force which arises, for example, through the movement of the push bars in the required direction of travel, to a signal controlling the patient support's movements. The push bars in the aforementioned patent can be equipped with a user presence detector, which is implemented, for example, using a force sensor. Alternatively, an air or liquid pressure sensor or capacity sensor can be used for this purpose.
Another known solution for propelling a patient support is implemented in the form of a motorized wheel capable of rotating around the vertical axis, using which the user can move the patient support in all directions. This solution is contained, for example, in patent application WO2009113009.
Motorized movement of a patient support entails danger in cases where the personnel stops controlling the patient support as a result of an accident or inattention. For these cases safety elements are included in the patient support control intended to brake the patient support. In this way the patient support is essentially braked for safety reasons in cases where the control of the patient support by the personnel is interrupted. So in U.S. Pat. No. 7,007,765 the patient support is braked by the friction of unpowered drive for propelling if the pressing of the mechanical switch is interrupted. One common means of braking a patient support is by shorting out the motor. Such a solution is described in patent CA2469462, for example. One problem of patient supports allowing motorized movement compared with conventional non-propelled patient supports is their more difficult manipulation in a tight space because the patient supports are often only capable of motorized movement in one or more directions and braking. Another shortcoming of patient supports with a motorized system is the necessity of drawing power from batteries even during a very small movement of the patient support. For systems in the known state of art it is not possible for the operator to make fine movements to a patient support using their own power if the main or another separate switch is not used, for disconnection of the shorting circuit of the motor or for activation of the clutch. For this reason it is very difficult for the user to switch from motorized movement to manual mode enabling the wheel to rotate freely.
The aim of the invention is to propose a solution for controlling the drive system of a hospital patient support providing for the hospital personnel safe and practical handling of the patient support in the motorized movement, manual movement and patient support braking modes. The proposed solution also provides more comfortable manipulation with the patient support. Safety of such a system is realized by pressing of two control buttons to activate the actuator and thus the activation of the system by the patient is prevented.
Another aim of the invention is to eliminate disadvantages of the system which requires pressing of the button and which is uncomfortable for the personnel in general and concurrently preserve high safety.
Another aim is to create such a concept using the capacity sensor which is power-saving. It means its power consumption is low, it includes standby mode for power saving and it provides safe solution of calibration.